Embodiments of the present invention relate generally to the treatment of a wound using a combined method consisting of negative (or reduced) pressure therapy and localized cooling. More specifically, the present invention relates to a system and a wound treatment method, which provides negative pressure and localized cooling at an open wound site while allowing continuous drainage of exudates from the wound.
Orthopedic extremity trauma accounts for 65 percent of combat wounds, over half of which are penetrating soft-tissue wound. Treatment of open wounds has long been a troublesome area in the practice of medicine. Some wounds are sufficiently large or infected that they are unable to heal spontaneously. In these complex cases, infection rates are directly related to the severity of the injury and the degree of contamination.
A recently published guideline for prevention of infection after combat-related injuries recommends rapid transport to higher level of care, immediate stabilization of fractures, early administration of antibiotics, repeated irrigation and debridement of wounds, and negative pressure wound therapy in the combat zone [1]. Even with these advancements in management of combat-related injuries, infections are still relatively common and morbid; resulting in delayed wound healing, multiple surgeries and administration of long term intravenous antibiotics. If unsuccessfully managed, these wounds can progress to chronic infections, and possibly lead to amputations of previously salvageable limbs.
The goals of current treatment protocol for infected wounds are simple:                a. minimize bacterial numbers through surgical debridement of contaminated tissue, and        b. alter the wound environment to directly kill bacteria or inhibit replication, usually via the administration of antibiotics.        
With the increasing prevalence of multi-drug resistant organisms (14, 15), further advancements in wound care need to be explored.
It is well known that there are optimal temperatures at which bacteria grow more readily. Deviations from this ideal temperature, both warming and cooling, can slow bacterial growth. For example, localized temperature elevation has been shown to decrease bacterial load in wounds (2, 3, 4). Localized cooling has been also shown to be beneficial in orthopedics by providing analgesic and anti-inflammatory properties, resulting in a decreased need for narcotics, less quadriceps inhibition, and a quicker recovery of function as compared to controls (9-13). However, total body hypothermia has been shown to hinder wound healing (5, 6). Prior research has shown that total body hypothermia is detrimental to wound healing, while others have demonstrated that a 3° to 6° C. drop in core temperature can be harmful in the setting of infection (4-8). With this level of systemic hypothermia, the host immune response is blunted, potentially leading to accelerated bacterial growth and overwhelming sepsis. The effects of this intervention on mortality in sepsis are still controversial (4, 7, 8). The effectiveness of localized cooling on infected wounds has not been studied.
Closure of surface wound involves inward migration of epithelial and subcutaneous tissue adjacent to the wound. This migration is ordinarily assisted through the inflammatory process, whereby blood flow is increased and various functional cell types are activated. Through the inflammatory process, blood flow through damaged or broken vessels is stopped by capillary level occlusion. Thereafter, cleanup and rebuilding operations may begin. Unfortunately, this process is hampered when a wound is large or has become infected. In such wounds, a zone of stasis (i.e. an area in which localized swelling of tissue restricts the flow of blood to the tissues) forms near the surface of the wound. Without sufficient blood flow, the epithelial and subcutaneous tissues surrounding the wound not only receive diminished oxygen and nutrients, but also are also less able to successfully fight bacterial infection. As a result, the body is less able to naturally close the wound.
Such difficult wounds were commonly addressed only through the use of sutures or staples. Although still widely practiced and sometimes effective, such mechanical closure techniques suffer a major disadvantage in that they produce tension on the skin tissue adjacent the wound. In particular, the tensile force required in order to achieve closure using sutures or staples may cause very high localized stresses at the suture or staple insertion point. These stresses can result in the rupture of the tissue at the insertion points, which eventually cause wound dehiscence and additional tissue loss.
Furthermore, some wounds harden and inflame to such a degree due to infection that closure by stapling or suturing is not feasible. Wounds not reparable by suturing or stapling generally require prolonged hospitalization, with its attendant high cost, and major surgical procedures, such as grafts of surrounding tissues. Examples of wounds not readily treatable with staples or suturing include large, deep, open wounds; decubitus ulcers; ulcers resulting from chronic osteomyelitis; and partial thickness burns that subsequently develop into full thickness burns.
As a result of these and other shortcomings of mechanical closure devices, one particular technique for promoting the body's natural healing process may be described as negative pressure wound therapy (NPWT). This technique involves the application of a reduced pressure, e.g. sub-atmospheric, to a localized reservoir over a wound. Sub-atmospheric pressure has been found to assist in closing the wound by promoting blood flow to the area, thereby stimulating the formation of granulation tissue and the migration of healthy tissue over the wound. This technique has proven effective for chronic or non-healing wounds, but has also been used for other purposes such as post-operative wound care.
In practice, the application to a wound of negative gauge pressure, commercialized under the designation “Vacuum Assisted Closure” (or “V.A.C® therapy). The related treatment methods and devices have been described in U.S. Pat. No. 4,969,880 issued on Nov. 13, 1990 to Zamierowski, as well as its continuations and continuations in part, U.S. Pat. No. 5,100,396, issued on Mar. 31, 1992, U.S. Pat. No. 5,261,893, issued Nov. 16, 1993, and U.S. Pat. No. 5,527,293, issued Jun. 18, 1996. Further improvements and modifications of the vacuum induced healing process are also described in U.S. Pat. No. 6,071,267, issued on Jun. 6, 2000 to Zamierowski and U.S. Pat. Nos. 5,636,643 and 5,645,081 issued to Argenta et al. on Jun. 10, 1997 and Jul. 8, 1997 respectively, U.S. Pat. No. 7,004,915, issued to Boynton et al. on Feb. 28, 2006, U.S. Pat. No. 7,611, 500, issued to Lina et al. on Nov. 3, 2009 and US Patent publication No. 20110213287 to Lattimore et al and US Patent publication No. 20090204085 to Biggie et al.
The general NPWT protocol provides for covering the wound with a flexible cover layer such as a polymeric film, for example, to establish a vacuum reservoir over the wound where a reduced pressure may be applied by individual or cyclic evacuation procedures. To allow the reduced pressure to be maintained over time, the cover layer may include an adhesive periphery that forms a substantially fluid tight seal with the healthy skin surrounding the wound.
Although some procedures may employ a micro-pump contained within the vacuum reservoir, most NPWT treatments apply a reduced pressure using an external vacuum source. Fluid communication must therefore be established between the reservoir and the vacuum source. To this end, a fluid port is coupled to the cover layer to provide an interface for an exudate conduit extending from the external vacuum source.
The embodiments of the present invention incorporate localized cooling therapy into current NPWT treatment system to stimulate and aid the treatment of infected or other open wounds.